Methods of assembling a valved aortic conduit

ABSTRACT

A valved conduit including a bioprosthetic aortic heart valve connected to a tubular conduit graft forming an ascending aorta. The conduit graft may attach to the heart valve in a manner that facilitates a redo operation in which the valve is replaced with another valve. A sewing ring may be pre-attached to the inflow end of the graft, and then the valve connected to a delivery holder advanced into the graft and secured to the sewing ring. Dry bioprosthetic valves coupled with conduit grafts sealed with a bioresorbable medium can be stored with the delivery holder.

RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/US2014/030639, filed Mar. 17, 2014, which was published inEnglish as International Patent Publication No. WO 2014/145811 A1 onSep. 18, 2014, which claims the benefit U.S. Patent Application No.61/802,201, filed Mar. 15, 2013, the entire disclosures of which areincorporated by reference herein.

FIELD OF THE INVENTION

The present invention generally relates to a prosthetic heart valveassembled with a flow conduit and, more particularly, to a pre-assembledaortic heart valve and aortic conduit that facilitates a redo operationwherein the valve is replaced with another valve.

BACKGROUND OF THE INVENTION

Heart valve disease continues to be a significant cause of morbidity andmortality, resulting from a number of ailments including rheumatic feverand birth defects. Cardiovascular disease is the number one cause ofdeath, killing more than 600,000 Americans each year. According to theAmerican Heart Association, more than five million Americans arediagnosed with heart valve disease each year. Heart valve disease canoccur in any single valve or a combination of the four valves, butdiseases of the aortic and mitral valves are the most common, affectingmore than five percent of the population. An estimated 85,000 aorticvalve replacement procedures are performed every year in the U.S.Worldwide, approximately 300,000 heart valve replacement surgeries areperformed annually. About one-half of these patients receivebioprosthetic heart valve replacements, which utilize biologicallyderived tissues for flexible fluid occluding leaflets.

Prosthetic heart valves may be implanted independently in one of theorifices or annuluses of the heart, or may be coupled to a flow conduitwhich extends in line with the valve a predetermined distance. In theso-called Bentall procedure the combined pathology of ascending aortaand aortic valve are replaced. There are a number of combined conduitsand valves on the market. Prior bioprosthetic valved conduits, as withbioprosthetic heart valves, are stored in a liquid preserving solution,and thus the conduits are formed of woven polyester without abioresorbable sealant. Although such conduits are suitable in certainsituations, and tend to seal relatively quickly in the body from tissueingrowth, too much blood can initially seep through their walls afterimplant which may be detrimental. Uncoated fabric such as polyethyleneterephthalate (PET) has a high leakage rate, and thus the surgeon needsto pre-clot the graft with patient's blood before use. Nevertheless,such grafts still produce unacceptable leaking. Others have proposedusing a non-bioresorbable sealant layer, such as silicone in U.S. PatentPublication No. 2008/0147171 to Ashton, et al., published Jun. 19, 2008,but such layered conduits tend to be relatively thick walled and notvery flexible, and so are not preferred.

Consequently, some surgeons prefer conduits or grafts in which poroustubular structures such as woven polyester (e.g., Dacron) areimpregnated with bioresorbable materials such as gelatin, collagen oralbumin. These conduits are not porous initially, and thus prevent bloodloss, but the sealant medium eventually degrades by hydrolysis whenexposed to water after implant and are replaced by natural tissueingrowth. Gelatin in the graft can also be treated in such a way as tocause cross links to form between the amino groups present in thegelatin molecules, which renders the gelatin more resistant tohydrolysis. Methods of forming such grafts are seen in U.S. Pat. No.4,747,848 to Maini, issued May 31, 1988.

Unfortunately, it is not possible to pre-assemble conduits or graftssealed using bioresorbable materials with bioprosthetic heart valvesbecause of storage complications. That is, the liquid sterilant in whichtissue valves are stored will eventually wash the bioresorbable sealingmedium (gelatin, collagen, albumin, etc.) out of the permeable conduitmaterial. Because of the benefits of using sealed conduits or grafts andthe positive attributes of bioprosthetic heart valves, some surgeonscouple the two components together at the time of surgery—post-storage.That is, technicians in the operating theater connect the sealed conduitwhich has been stored dry to the bioprosthetic heart valve which hasbeen stored wet. Such assemblies can be seen in U.S. Pat. No. 8,512,397to Rolando, et al., issued Aug. 20, 2013, and in U.S. Pat. No. 7,575,592to Woo, et al., issued Aug. 18, 2009. The sealed conduit may be sewn tothe sewing ring of the bioprosthetic heart valve, or some other form ofquick-connect coupling can be provided, such as seen in U.S. PatentPublication No. 2006/0085060 to Campbell, published Apr. 20, 2006.

Once implanted, many valved conduits require a valve re-replacement, or“redo” procedure, such as if the bioprosthetic leaflets calcify.Unfortunately, many of the prior valved conduit designs are sointegrated that the entire assembly must be removed, rather than justthe non-functioning valve.

Despite these advances, there is a need for a valved conduit having abioprosthetic tissue valve which is simpler to implant and whichfacilitates replacement of the valve if necessary.

SUMMARY OF THE INVENTION

A valved conduit including a bioprosthetic aortic heart valve connectedto a tubular conduit graft forming an ascending aorta. The conduit graftattaches to the heart valve in a manner that facilitates a redooperation in which the valve is replaced with another valve. Variousconnection configurations are provided, some in which the conduit graftis sewn to the heart valve sewing ring, some in which there are twosewing rings, and some which utilize more mechanical snap-fit or lockingring connections.

The present application discloses a valved conduit including abioprosthetic heart valve and a tubular conduit, preferably sealed witha bioresorbable material. The bioprosthetic heart valve may haveprosthetic tissue that has been treated such that the tissue may bestored dry for extended periods without degradation of functionality ofthe valve. The bioprosthetic heart valve may have separate bovinepericardial leaflets or a whole porcine valve. The heart valve may besewn within the conduit, sewn to the end of the conduit or coupledthereto with a snap-fit connection to limit handling of the two treatedcomponents and provide a hemostatic seal with minimal assemblycomplexity. Preferably the attachment configuration facilitates a redooperation in which the valve can be easily excised from within the graftand replaced.

In one preferred embodiment, a valved conduit comprises a subassembly ofa conduit graft and an annular sewing ring. The conduit graft includes alongitudinal tubular portion between an upper end and a lower end, thelower end having a collar portion. The sewing ring comprising an innercore and an outer fabric covering, the sewing ring being positionedadjacent the lower end of the conduit graft whereby the collar portioncontacts and is secured to an inner wall of the annular sewing ring. Thesubassembly of the conduit graft and sewing ring is independently leaktested. A prosthetic heart valve in the valved conduit has an innersupport frame covered with fabric and defining a flow orifice and aplurality of leaflets extending inward from the support frame to ensureone-way blood flow through the heart valve. The heart valve ispositioned within the lower end of the conduit graft and the fabriccovering the support frame extends downward in a tubular segment and isfolded radially outward underneath the subassembly of the conduit graftand sewing ring and secured thereto with sutures. Finally, a holderattaches to the heart valve and extends from the heart valve out of theupper end of the conduit graft.

In the valved conduit described above, the collar portion may have anundulating shape around its circumference with peaks and valleys, andthe sewing ring also has an undulating shape around its circumferencewith peaks and valleys, wherein the peaks and valleys of the collarportion align with the peaks and valleys of the sewing ring. The conduitgraft may be secured to the sewing ring using sutures, by welding, orusing an intermediate band which is secured to both the conduit graftand sewing ring. The heart valve leaflets are desirably made ofbioprosthetic tissue, and the conduit graft preferably comprises atubular matrix impregnated with gelatin. The heart valve leaflets aremore preferably formed of bovine pericardium that has been cross-linkedusing glutaraldehyde or other aldehyde containing agents, treated with acapping agent, and is dehydrated with a glycerol solution.

A method of assembling a valved conduit disclosed herein, comprises thefollowing steps:

forming a subassembly of a conduit graft and an annular sewing ring, theconduit graft comprising a longitudinal tubular portion between an upperend and a lower end, the lower end having a collar portion, the sewingring comprising an inner core and an outer fabric covering, the step offorming comprising positioning the sewing ring adjacent the lower end ofthe conduit graft so that the collar portion contacts an inner wall ofthe annular sewing ring and securing the collar portion thereto;

leak testing the subassembly of the conduit graft and sewing ring;

providing a prosthetic heart valve having an inner support frame coveredwith fabric and defining a flow orifice and a plurality of leafletsextending inward from the support frame to ensure one-way blood flowthrough the heart valve, the fabric covering the support frame extendingdownward in a tubular segment;

attaching a holder to the heart valve; and

positioning the heart valve within the lower end of the leak testedsubassembly of the conduit graft and sewing ring and folding the tubularsegment of the fabric covering radially outward underneath thesubassembly and secured the tubular segment thereto with sutures, theholder having a length sufficient to extend from the heart valve out ofthe upper end of the conduit graft.

A further understanding of the nature and advantages of the presentinvention are set forth in the following description and claims,particularly when considered in conjunction with the accompanyingdrawings in which like parts bear like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained and other advantages and featureswill appear with reference to the accompanying schematic drawingswherein:

FIG. 1 is an exploded view of the combination of a bioprosthetic heartvalve coupled to an aortic conduit graft of the present application toform a valved conduit;

FIG. 2 is an elevational view of a valved conduit of the presentapplication coupled to a delivery handle;

FIG. 3 is an exploded view of the delivery handle and valved conduitshowing primary components of the bioprosthetic heart valve;

FIG. 4 is a perspective view of the lower or inflow end of the valvedconduit illustrating an exemplary sewing ring minus an outer fabriccovering, and FIG. 4A is a radial sectional view through a lower end ofthe valved conduit taken through a cusp portion of the exemplary sewingring, this time showing the outer fabric covering;

FIG. 5 is a perspective view of the exemplary sewing ring;

FIGS. 6A and 6B are radial sectional views through a lower end of avalved conduit showing alternative configurations of attachment betweenthe conduit and valve;

FIG. 7 is an elevational view of the inflow end of a valved conduit, andFIGS. 7A and 7B are schematic views of two different stitch patternsthat can be used between the conduit and valve;

FIG. 8 is a radial sectional view through a lower end of a valvedconduit wherein the bottom end of the conduit is wrapped and sewntogether with a fabric tab of the heart valve;

FIGS. 9-10 are radial sectional views through a lower end of the valvedconduit wherein the conduit attaches to a secondary sewing ring which,in turn, attaches to a primary sewing ring of the heart valve;

FIG. 11 is a radial sectional view through a lower end of the valvedconduit wherein the conduit is folded and attaches to the heart valvesewing ring, and also to a secondary sewing ring;

FIG. 12 is a radial sectional view through a lower end of the valvedconduit wherein the conduit attaches to a sewing band which, in turn,attaches to a fabric tab of the heart valve through a protective cap;

FIG. 13 is a radial sectional view through a lower end of the valvedconduit wherein the conduit attaches to the secondary sewing ring which,in turn, attaches to a primary sewing ring of the heart valve via a ringadapter having cutting guides;

FIG. 14 is a perspective view of the ring adapter from FIG. 13schematically showing the path of sutures used to secure the ring to thevalved conduit, and FIG. 14A is an enlarged view of one cutting guidefrom the top of the ring adapter;

FIG. 15 is a partial exploded view of an alternative valved conduitassembly wherein an adapter ring is used between the conduit and heartvalve, and FIG. 15A is a radial sectional view through a lower end ofthe valved conduit showing the position of the adapter ring and how itattaches to the conduit and valve;

FIGS. 16A-16C are radial sectional views through a lower end of a valvedconduit wherein the heart valve has a dual sewing ring and the lower endof the conduit attaches to different locations thereon;

FIG. 17 is an exploded view of a heart valve having a dual sewing ring,and FIG. 17A is an assembled view of the heart valve;

FIG. 18A is a longitudinal sectional view through a lower end of aconduit having a tubular hem enclosing a locking ring, while FIG. 18Billustrates an exemplary form of a locking ring and FIG. 18C is a radialsectional view through a lower end of a valved conduit in which thelocking ring at the bottom end of the conduit is held within anoutwardly opening channel secured to the heart valve;

FIG. 19A is a radial sectional view through a lower end of a valvedconduit showing a locking ring hemmed to the lower end of the conduitand secured within an inwardly opening locking channel secured to theheart valve, while FIG. 19B is a longitudinal sectional view through alower end of the conduit illustrating the tubular hem;

FIGS. 20A-20D illustrate variations of locking rings for use with theconfiguration shown in FIG. 19A;

FIGS. 21A and 21B show a locking ring at the bottom of a conduit matingwith an alternative inwardly-facing channel of an exemplary heart valve;

FIG. 22 is a radial sectional view through a lower end of a valvedconduit showing a locking ring hemmed to the lower end of the conduitand an adjustable clamp provided on the heart valve;

FIGS. 23A and 23B are exploded and assembled views, respectively, of analternative connection arrangement between a conduit graft and aprosthetic heart valve utilizing a wire coil that passes through a hemof the conduit graft;

FIGS. 24A and 24B are alternative configurations of a sewing ring foruse with the connection arrangement of FIGS. 23A and 23B;

FIG. 25 is an exploded perspective view of a prosthetic heart valvehaving a pair of coupling rings attached thereto;

FIG. 26 is an exploded perspective view of a conduit graft having alocking ring on a lower end above the assembled prosthetic heart valveof FIG. 25, and FIGS. 26A and 26B are plan and sectional viewsillustrating the engagement between the locking ring and the couplingrings of the prosthetic heart valve;

FIGS. 27A-27C are perspective and sectional views of an alternativeprosthetic heart valve having a connection arrangement utilizing lockingtabs on the heart valve that mate with channels in a sewing ring cuff;

FIG. 28 illustrates the locking ring of the embodiment of FIGS. 27A-27Cand an outer anchoring member that forms a part of the lower end of aconduit graft;

FIG. 29A is a radial sectional view of the engagement between the sewingring cuff and an exemplary outer anchoring ring having the anchoringmember therein, and FIG. 29B is a radial sectional view showing theassembly of FIG. 28 connected to a conduit graft, and also illustratingthe heart valve engaging the sewing ring cuff;

FIG. 30 is a perspective view of a still further connection arrangementbetween a conduit graft and a prosthetic heart valve utilizing anintermediate band attached to the graft and having a crown-shaped loweredge while FIG. 30A is a closeup of a portion of the assembly;

FIG. 30B is an enlargement of one edge of the intermediate band takenfrom FIG. 30A, and FIG. 30C is a section view through a cutting wellthereon;

FIG. 31A is a perspective view of the intermediate band from theassembly of FIG. 30, and FIG. 31B is an alternative band havingcrown-shaped upper and lower edges;

FIGS. 32A-32D are sectional and perspective views of one embodiment of asubassembly of a conduit graft and annular sewing ring connectedtogether via an intermediate band;

FIG. 33A is a perspective exploded view of an alternative configurationof a valved conduit system;

FIG. 33B is a perspective view showing a prosthetic heart valve beingcoupled to a sewing ring/conduit graft subassembly to form the valvedconduit system;

FIGS. 34A-34D are sectional and perspective views of several initialsteps in the pre-assembly of the sewing ring to the conduit graft ofFIGS. 33A-33B;

FIGS. 35A-35C are sectional and perspective views of several furthersteps in the pre-assembly of the sewing ring to the conduit graft ofFIGS. 33A-33B;

FIGS. 36A-36D are perspective and sectional views of several preliminarysteps for coupling the prosthetic heart valve to the sewing ring/conduitgraft subassembly of FIG. 33;

FIGS. 37A-37D are perspective and sectional views of several final stepsfor forming the valved conduit system of FIG. 33A;

FIG. 38 shows an alternative type of stitch that may be used between theconduit graft and sewing ring;

FIG. 39 shows the addition of a sealant that may be used between theconduit graft and sewing ring;

FIGS. 40A and 40B show alternative stitches that may be used between theconduit graft and sewing ring;

FIGS. 41 and 42 schematically illustrate a process for shaping tissue toform an aortic root portion of a conduit graft for use in thecombinations herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Described herein are a number of two-piece valved conduits including aprosthetic heart valve and a conduit graft that facilitate valve redooperations. That is, the heart valve within the valved conduit sometimesbecomes calcified and must be replaced. The combinations disclosedherein provide easy to remove valves.

FIG. 1 is an exploded view of an exemplary valved conduit VC comprisingthe combination of a bioprosthetic heart valve 20 coupled to an aorticconduit graft 22. As suggested schematically, the prosthetic heart valve20 is positioned within one end of the conduit graft 22. Such a valvedconduit VC may be used for replacing a native aortic valve and theascending aorta. Of course, certain principles disclosed herein wouldalso apply to replacement of the pulmonary valve and the pulmonaryartery.

The heart valve 20 includes a rigid or semi-rigid stent supporting aplurality of flexible leaflets 24 (typically three) that are mounted toa peripheral stent structure 26 and form fluid occluding surfaces withinthe valve orifice to form a one-way valve. The stent structure 26includes a plurality of generally axially extending commissures 28circumferentially distributed around the valve between and in the samenumber as the number of leaflets 24. Although not shown, additionalcomponents of the heart valve 20 typically include an inner stent and/orwireform support structure that provide a structural skeletonsurrounding an inflow orifice and extending up the commissures 28. Theinner components of the heart valve 20 may be made of suitable metal orplastic. As is well known, adjacent flexible leaflets 24 connect to andextend upward to meet along each of the commissures 28. In theillustrated embodiment, the structural components of the heart valve 20support each flexible leaflet 24 along a valve cusp 30 and along twocommissure 28 edges. A free edge 25 of each leaflet 24 extends inwardtoward a central flow orifice and coapts, or mates, with the free edgesof the other leaflets, as shown. The valve orifice is oriented around anaxis along an inflow-outflow direction through the valve. The valvecommissures 28 project in the outflow direction, with the convex valvecusps 30 extending in the inflow direction between adjacent commissures.A sewing ring 32 on the inflow end conforms to the undulating contoursof the valve cusps, or defines a generally circular, planar ring. Thepresent application should not be considered limited to a particularvalve construction unless explicitly stated herein. Also, it will beunderstood that the sewing ring 32 may be conventional, that isunmodified from an existing heart valve sewing ring, or may be modifiedas described below.

The conduit graft 22 defines a generally tubular structure that extendsfrom an inflow end 42 to an outflow end 44. In the embodiment shown, thevalve 20 is associated with the conduit graft 22 in such a way that thevalve leaflets 24 control flow of blood through the conduit bypermitting blood flow into the conduit (e.g., blood flow into the aorta,when the conduit is used for aortic replacement) while preventing flowof blood out of the conduit in the opposite direction (i.e., back intothe left ventricle of the patient when used for aortic replacement).

The illustrated conduit graft 22 is particularly suited for attachmentwithin the aortic annulus and ascending aorta, and as such closelymatches the aortic root anatomy and includes an enlarged region or bulge46 close to the inflow end 42 that conforms to the sinuses of valsalvajust above the aortic annulus. In the preferred embodiment, the conduitgraft 22 comprises a tubular textile structure, such as Dacron, sealedwith a bioresorbable medium such as gelatin or collagen. A majority ofthe conduit graft 22 includes a circumferentially corrugated (i.e.,grooved) or pleated sidewall that provides longitudinal flexibility andradial compressibility while ensuring that the graft does not undulyradially expand under the pressure of blood flowing therethrough. Theenlarged region or bulge 46 may be configured with longitudinalcorrugations that are more radially expandable than the circumferentialpleats to allow expansion at that location into the Valsalva sinuses.The conduit graft 22 desirably has a length of from a few centimeters to10-12 centimeters.

In one embodiment, the conduit graft 22 may be a Vascutek GelweaveValsalva™ Grafts gelatin sealed, aortic root graft that is indicated foraortic root replacement using valve sparing or replacement techniques,and available from the Vascutek business of Terumo CardiovascularSystems Corporation of Ann Arbor, Mich. As explained below, the use of abioresorbable medium to provide a temporary seal to the implanted graftis preferred and may be preassembled with the exemplary bioprostheticheart valves disclosed herein. However, the exemplary bioprostheticheart valves may also be pre-assembled with other sealed grafts orconduits, such as those that utilize non-bioresorbable material. Itshould be understood that unless excluded by claim language, a varietyof conduits are contemplated.

FIG. 2 shows the valved conduit VC coupled to a delivery handle 50,while FIG. 3 is an exploded view of the components. The delivery handle50 includes an ergonomic grip 52 on a proximal end, and a shaft 54extending distally and terminating in a valve holder 56. The valveholder 56 is shown schematically, and maybe any one of a variety ofholder types. For example, the holder 56 may include three outwardlyprojecting arms which contact and are attached to tips of thecommissures 28 of the heart valve 20.

The heart valve 20 is shown exploded and missing a fabric covering, witha stent and leaflet subassembly 60 above an exemplary enlarged andmodified sewing ring 62. It should be noted that the lower end of thestent and leaflet subassembly 60 has a gently undulating configurationwith three downwardly-bowed cusps 64 alternating with upward rises 65 atthe location of the commissures 28. Likewise, the sewing ring 62 has anundulating configuration to match the lower end of the stent and leafletsubassembly 60, as will be described in more detail below.

An assembly process comprises attaching the valve holder 56 to theprosthetic heart valve 20 prior to attachment to the conduit graft 22.The grip 52 of the handle 50 is inserted from the inflow end (rightside) of the conduit graft 22 and passed therethrough until the sewingring 62 contacts the graft and the two are sewn together. The presentapplication discloses a number of ways for coupling the prosthetic heartvalve 20 to the conduit graft 22, and thus this assembly process mayapply to any of the embodiments described herein.

FIG. 4 is an enlargement of the lower or inflow end of the valvedconduit VC illustrating the exemplary sewing ring 62 minus an outerfabric covering. As also seen in isolation in FIG. 5, the sewing ring 62comprises a generally annular waffle-like member of soft,suture-permeable material, such as silicone. As also seen in the radialcross-section of FIG. 4A the sewing ring 62 has a central, generallyvertical wall 70, an outer flange 72, and an inner ledge 74. Both theouter flange 72 in the inner ledge 74 connect to a lower end of thecentral vertical wall 70 and project therefrom. The outer flange 72extends outward at a slight upward angle, and connects to the verticalwall 70 via a series of circumferentially-oriented ribs 76, which defineopen cells 78 therebetween. The inner ledge 74 extends generallyradially inward and has no such ribs.

With reference to FIG. 4A, internal components of the heart valve 20 areshown in sectional view. More specifically, the heart valve 20 includesan inner stent structure which in the illustrated embodiment includestwo concentric bands 80, 82 that are enclosed in fabric 84 which isbunched or rolled into an outwardly-directed sewing tab 86. An outeredge of one of the leaflets 24 is sandwiched between the top of thestent structure and the bottom of a cloth-covered wireform 90. Morespecifically, the wireform 90 has a cloth covering with free ends thatare folded together to form a sewing flap 92. Stitches (not shown)connect the sewing flap 92 to the sewing tab 86 below it.

The heart valve is positioned within the sewing ring 62, and the stentstructure and sewing ring 62 are surrounded by an encompassing fabriccover 94. More specifically, the lower end of the stent structureincluding the two concentric bands 80, 82 abuts an outer end 96 of theinner ledge 74 of the sewing ring 62. The inner ledge 74 extends inwardfrom the vertical wall 70 a sufficient distance such that the sewing tab86 projects into the space therebetween. Conventional sewing rings donot have such a large inward ledge 74, and typically do not extendoutward as far as the outer flange 72. The lower end of the conduitgraft 22 attaches to the upper end 97 of the vertical wall 70 withstitches 98. Because of the space created between the heart valve 20 andthe vertical wall 70, a surgeon can insert a scalpel therebetween toeasily excise the heart valve if necessary, such as in a redo operation.That is, the radial extent of the inner ledge 74 creates the spacebetween the heart valve and the sewing ring which facilitates the redooperation.

It should be noticed that the outer flange 72 of the sewing ring 62travels in an undulating path which is more pronounced than the pathcircumscribed by the upper end 97 of the vertical wall 70. In apreferred embodiment, the conduit graft 22 is generally circular andplanar on its lower end prior to attachment to the heart valve.Alternatively, as described below, the lower end of the conduit graft 22may be cut so as to match the undulating shape of the upper end 97 ofthe vertical wall 70 of the sewing ring 62. Because the upper end 97 ofthe vertical wall 70 has a very gentle scalloped or undulatingconfiguration, a minimum amount of wrinkling or puckering of the fabricof the conduit graft is seen when the lower end is attached to thevertical wall 70. On the other hand, the more pronounced undulation ofthe outer flange 72 better fits the undulating shape of the aorticannulus. That is, in use, the surgeon attaches the outer flange 72 ofthe sewing ring 62 to the aortic annulus using an array of pre-installedparachute sutures, as is well known in the art.

FIGS. 6A and 6B are radial sectional views through a lower end of avalved conduit VC showing alternative configurations of attachmentbetween the conduit graft 22 and valve 20. The heart valve 20 is ofconventional construction wherein the sewing ring 32 projects outward atan angle from a lower end of the stent structure. The sectionsillustrated in FIGS. 6A and 6B are taken through cusps of the heartvalves.

In FIG. 6A, the conduit graft 22 extends downward to a line just insidethe outer edge of the sewing ring 32, and is attached thereto usingstitches 100. A length of the conduit graft 22 then wraps around thesewing ring 32 and terminates at a lower end 102. Although not shown,stitches are typically provided at spaced locations to maintain theconformal contact between the conduit graft and sewing ring, as shown.Again, a space 104 between the conduit graft 22 and the valve 20facilitates cutting the conduit graft just above the heart valve for aredo operation. A similar configuration is shown in FIG. 6B, but aseries of pleats or folds 106 are formed in the fabric of the conduitgraft 22 at the outer edge of the sewing ring 32. This provides anextension of the sewing ring which helps during the implantationoperation. That is, there is a greater amount of material through whichto pass sutures, which reduces the chance of passing the needle throughthe delicate areas of the heart valve.

FIG. 7 again shows the inflow end of a valved conduit VC, and FIGS. 7Aand 7B are schematic views of two different stitch patterns that can beused between the conduit graft and heart valve. In FIG. 7A, a backstitchtechnique is utilized which attaches the crease of the conduit smoothlyand firmly to the sewing ring, leaving no gap that could cause leakageat the attachment site. The backstitch comprises sewing a first stitch(1) about 1 mm long circumferentially around the crease of the conduit,then sewing down (2) through the sewing ring and out of the coveringcloth on the proximal side of the sewing ring. The needle is theninserted at (3) back into the sewing ring through the same hole of thecloth and exits ½ mm back from the previous stitch on the conduit.Stitch (4) is forward 1 mm. This pattern is then repeated around theentire circumference of the assembly. The use of this sewing techniqueis advantageous in that it avoids exposed sutures showing on the bottomof the sewing ring, and minimizes the “puckering” of the sewing ringcloth on the proximal end of the valve.

Alternatively, the embodiment in FIG. 7B uses an in-and-out stitchtechnique which improves assembly speed and requires fewer stitches toattach the conduit to the sewing ring. The process involves sewing onestitch (1) about 1.5 mm long circumferentially along the fold of theconduit, and then sewing down (2) through the sewing ring. A 1.5 mmstitch (3) is then placed under the stent cloth and passed through thesewing ring to exit (4) back on the fold of the conduit, repeating thispattern around the entire circumference of the assembly.

FIG. 8 is conduit graft/valve connection in which a lower end of theconduit graft 22 is wrapped and sewn together with a rolled sewing tab86 of the heart valve 20. This configuration requires assembly of thegraft and valve together at the time of manufacture, whereas some of theembodiments described herein can utilize fully fabricated heart valvescoupled to secondary structure.

FIGS. 9-10 are radial sectional views through a lower end of the valvedconduit wherein a secondary sewing ring 110 is utilized for connectingthe conduit graft to the valve. The valve is conventional, with anoutwardly angled sewing ring 32. In FIG. 9, the secondary sewing ring110 attaches to the bottom side of the primary sewing ring 32 with, forexample, stitches. The secondary sewing ring 110 extends the length ofthe primary sewing ring 32, but a portion projects outward and the lowerend of the conduit graft 22 attaches thereto with stitches, for example.In FIG. 10, the secondary sewing ring 110 only overlaps about the outerhalf of the primary sewing ring 32, and a greater width extends outwardto which the conduit graft 22 is attached. In each of the configurationsshown in FIGS. 9-10, the secondary sewing 110 is used to provide aplatform used to sew the assembly to the aortic annulus. Consequently,the redo operation is made relatively simple by severing the secondarysewing ring 110 just inside the conduit graft 22.

FIG. 11 shows a secondary sewing ring 110 attached to the bottom end ofthe conduit graft 22, which, in turn, attaches to the lower side of theprimary sewing ring 32. A fold 112 in the fabric of the conduit graftprovides a flap to which the primary sewing ring 32 is sewn. In FIG. 11the secondary sewing ring 110 is also used as a platform to sew to theaortic annulus, but the redo operation is accomplished by severing theprimary sewing ring 32.

FIG. 12 illustrates a configuration where the valved conduit 22 attachesto a sewing band 120 which, in turn, attaches to a fabric sewing tab 86of the heart valve 20. In this embodiment, the heart valve 20 includesno primary sewing ring. The sewing band 120 has a generally conicalconfiguration with a protective cap 122 on an inner end. The protectivecap 122 may be made of a number of different materials, preferably apolymer such as Delrin. Stitches 124 are used to connect the sewing band120 to the sewing tab 86 of the heart valve 20, while the lower end ofthe conduit graft 22 is also sewn to a location on the sewing band whichleaves a relatively large portion for use to sew the assembly to theaortic annulus. In a redo operation, the surgeon need only sever thestitches 124 connecting the sewing band 120 to the heart valve 20, andthe protective cap 122 helps delineate and protect the inner end of thesewing band 120 from damage.

FIG. 13 shows the primary sewing ring 32 of a heart valve 20 attached toa secondary sewing ring 130 via a ring adapter 132 having cutting guides134. FIG. 14 is a perspective view of the ring adapter 132 andschematically shows the path of sutures 136 used to secure the ring tothe sewing ring. FIG. 14A is an enlarged view of one cutting guide 134from the top of the ring adapter 132. The ring adapter 132 comprises agenerally flat (or undulating if desired) disc-shaped annulus whichconforms to the top side of the primary sewing ring 32. Adjacent sutures136 are tied to each other above the surface of the ring adapter 132 atspaced locations 138 around the circumference. Each suture 136 extendsclockwise or counterclockwise, passing down through one of a pair ofanchor holes 140 and looping downward through the primary sewing ring 32and through a portion of the secondary sewing ring 130, such as shown at142 in FIG. 14. The sutures 136 then comes up through a second hole 144and crosses over the cutting guide 134. The suture passes down through athird hole 146 and again loops through the primary sewing ring 32 andsecondary sewing ring 130. Finally, the sutures 136 come up throughanother of the anchor holes 140 and ties to an adjacent suture. Thisarrangement permits the detachment of the heart valve from the secondarysewing ring 130, which is attached to the annulus and the conduit graft22, by simply severing each of the separate sutures 136 at the cuttingguides 134.

FIG. 15 is a partial exploded view of an alternative valved conduitassembly wherein an adapter ring 150 is interposed between the conduitgraft 22 and heart valve 22. As seen in FIG. 15A, the adapter ring 150is positioned on the upper or outflow side of the heart valve sewingring 32 and attaches thereto with a line of stitches 152. The adapterring 150 includes a lower flange 154 that conforms to the top of thesewing ring 32 (flat or undulating). An inner, generallyaxially-oriented flange 156 projects upward and the bottom end of theconduit graft 22 connects thereto, such as with stitches through a lineof suture holes 158 (FIG. 15). The adapter ring 150 also includes anintermediate flange 160 which generally projects outward parallel to thelower flange 154 such a circumferential somewhat V-shaped gap 162 isformed therebetween. The line of stitches 152 crosses the gap 162 andthrough holes 164 in the intermediate flange such that a surgeon candisconnect the heart valve 20 from the conduit graft 22 and adapter ring150 by passing a scalpel into the gap. The adapter ring 150 may be madeof a suitable rigid polymer, such as Delrin or nylon, so that thescalpel does not easily pass through it.

FIGS. 16A-16C are radial sectional views through a lower end of a valvedconduit wherein the heart valve 20 has a dual sewing ring 170 formed bya primary sewing ring 32 and a secondary sewing ring 172 attachedoutward therefrom. The lower end of the conduit graft 22 connects to theprimary sewing ring 32 at its upper side (FIG. 16A), to its outer end(FIG. 16B), or to its lower side (FIG. 16C). In each case, the secondarysewing ring 172 provides a relatively large platform which the surgeoncan use to sew the assembly to the surrounding aortic annulus.

FIG. 17 is an exploded view of a heart valve having the dual sewing ring170, and FIG. 17A is an assembled view of the heart valve 20. Both theprimary sewing ring 32 and the secondary sewing ring 172 are generallyflat conical pieces of suture-permeable material, such as silicone,covered with cloth. As seen in the section views of FIGS. 16A-16C, bothsewing ring 32, 172 attached around substantially thin seam lines sothat they can easily pivot with respect to one another, and with respectto the rest of the heart valve. In particular, the secondary sewing ring172 can be pivoted outward so the surgeon can easily pass suturesthrough it during implantation.

FIG. 18A is a longitudinal sectional view through a lower end of aconduit graft 22 having a tubular hem 180 formed on a lower endenclosing a locking ring 182. For example, FIG. 18B shows a C-shapedlocking ring 182 having a hollow throughbore within which a drawstring184 may be placed. FIG. 18C is a sectional view in which the lockingring 182 at the bottom end of the conduit graft 22 is held within anoutwardly opening channel 190 of the ring member 192 secured to a heartvalve 20. For example, the ring member 192 may be metallic and may bewelded to an outer metal band 82 of the heart valve, or the ring member192 may be connected with sutures, adhesive, or other such solutions.The conduit graft 22 couples to the heart valve 20 by interferencebetween the locking ring 182 and the channel 190. In particular, theC-shaped ring 182 may have a relaxed shape with a larger diameter thanthe diameter of the channel 190, wherein tensioning the drawstring 184after positioning the lower end of the conduit graft 22 outside of thering member 192 constricts the ring 182, thus causing it to engage thechannel 190. Alternatively, the C-shaped locking ring 182 may have arelaxed diameter that is approximately the same as the channel 190, andmay be flexed apart to allow it to pass over the valve structure andenter the channel 190 from its elastic recoil. The locking ring 182desirably has an undulating shape as shown to match the undulating shapeof the channel 190 that follows the ring member 192, or the two matingcomponents may be circular/planar. In a valve redo operation, thesurgeon need only disengage the locking ring 182 from the channel 190,and remove the valve. The C-shaped ring 182 is made of a metal orhigh-density plastic flexible enough to be compressed to a tighterradius, such as when tension is applied to the drawstring 184.

FIG. 19A illustrates a locking ring 200 hemmed to the lower end of aconduit graft 22 and secured within an inwardly opening locking channel202 of a valve ring 204 secured to the heart valve 20. In thisembodiment, it is the outward force of the locking ring 200 that couplesthe two parts together. FIG. 19B shows the lower end of the conduitgraft 22 illustrating the tubular hem 206. The locking ring 200 iseither discontinuous (e.g., C-shaped) and threaded through an opening inthe tubular hem 206, or maybe continuous and enclosed when the hem isformed.

FIGS. 20A-20D illustrate variations of locking rings 200 for use withthe configuration shown in FIG. 19A. For example, a simple C-shaped ring210 in FIG. 20A may be squeezed to reduce its diameter and allow itspassage into the channel 202 of the valve ring 204. FIG. 20B illustratesa coil spring-type locking ring 212 which is relatively flexible andeasily passes into the channel 202, but has sufficient resiliency toretain the conduit graft 22 together with the heart valve 20. FIG. 20Cillustrates a discontinuous locking ring 214 with overlapping featuresdesigned to slide over each other under compression or expansion. Theprogression shows the shape of the ring 214 from when it is compressed(above) to its relaxed shape (below) with a larger diameter which locksin the channel 202. Likewise, FIG. 20D illustrate another locking ring216 with overlapping features that somewhat resembles a keyring. Again,the illustration on the top is compressed for entry into the channel202, while the figure on the bottom shows the ring 216 expanded. Thecontinuous locking rings are preferred because they do not formstructural gaps at the lower end of the conduit graft which might permitparavalvular leakage.

FIGS. 21A and 21B show a locking ring 220 at the bottom of a conduitgraft 22 mating with an alternative inwardly-facing channel 222 of anexemplary heart valve. Instead of a solid ring forming a channel, thechannel 222 is formed by a rigid ring 224 embedded within the sewingring 226 of the valve. The locking ring 220 at the bottom of the conduitgraft is compressed, as seen in FIG. 21A, so that it can fit within thechannel 222, and then released so that it expands outward to its relaxedshape into the channel, as seen in FIG. 21B.

FIG. 22 illustrates a still further embodiment wherein a circularlocking ring 230 hemmed to the lower end of the conduit graft 22 iscaptured by an adjustable clamp 232 provided on the heart valve 20. Forexample, the adjustable clamp 232 may comprise a drawstring 234 capturedwithin a tubular hem of a piece of fabric 236 connected to the valvesewing ring 32. Alternatively, the element 234 contained within thehemmed fabric 236 may be a discontinuous ring or spring member which canbe expanded to allow entry of the locking ring, 230 then released toconstrict inward, thus capturing the locking ring and conduit graft 22.Again, in a reverse procedure, the surgeon can expand the adjustableclamp 232 and remove the valve from the conduit graft in a redooperation.

FIGS. 23A and 23B are exploded and assembled views, respectively, of analternative connection arrangement between a conduit graft 22 and aprosthetic heart valve 20. A wire coil 240 anchors at one end to anupper side of the sewing ring 32 of the heart valve, and then passesthrough an opening in and around a hem 242 of the conduit graft. As seenin FIG. 23B, a loop 243 on the free end of the wire coil 240 catches ona small hook 244 or other such anchor also attached to the sewing ring32. A number of spaced sutures 246 are provided to hold down the lowerend of the graft 22 having the coil 240 therein.

Grooves or other such depressions in the upper surface of the sewingring 32 may be provided to help capture the lower end of the graft 22.For instance, FIGS. 24A and 24B show alternative configurations of asewing ring 250, the former of which provides a shallow groove 252 andthe latter of which provides a deeper pocket 254. The sutures 246 loopedaround the coil 240 can be tensioned to pull the lower end of the graftinto the groove 252 or pocket 254, which helps prevent leakage betweenthe two.

FIG. 25 illustrates a prosthetic heart valve 20 with a pair of couplingrings 260, 262 that attach thereto. More particularly, a lower couplingring 260 includes a central aperture 264 larger than the commissure andleaflet structure such that the ring rests on the sewing ring 32.Likewise, the upper coupling ring 262 has a similarly-sized centralopening 265 and sits on top of the lower coupling ring 260. The lowerring 260 has three recesses 266 evenly distributed on its upper surfaceand opening to the central aperture 264. The recesses 266 are generallyshallow, arcuate, and flat, and feature a small bump 268 projectingupward in the middle. The upper coupling ring 262 includes threeequidistantly spaced notches 270 that open inward to the central opening265. The notches 270 register over the recesses 266 on the lower ring260. Both of the coupling rings 260, 262 include a plurality of sutureholes distributed around their peripheries to permit attachment to thesewing ring 32.

FIG. 26 shows the prosthetic heart valve 20 with the two coupling rings260, 262 attached thereto. A conduit graft 22 exploded above the valvehas a locking ring 272 attached to a lower end thereof. The locking ring272 features three outwardly projecting tabs 274 that are sized toregister with the notches 270 in the upper coupling ring 262. That is,the conduit graft 22 attaches to the heart valve 20 by engaging thelocking ring 272 with the coupling rings 260, 262.

FIGS. 26A and 26B are plan and sectional views illustrating theengagement between the locking ring 270 and the coupling rings 260, 262.Each of the tabs 274 extends downward through a corresponding notch 270in the upper coupling ring 262 and into one of the recesses 266 in thelower coupling ring 260. Rotating the assembly of the conduit graft 22and locking ring 270 causes each of the tabs to rotate within thecorresponding recess 266, eventually camming over the small bump 268 soas to be captured therein. For a redo operation, the procedure isreversed with the conduit graft 20 and locking ring 270 being rotated inthe opposite direction to overcome the resistance of the bumps 268 andpermit the tabs 274 to exit from the notches 270.

FIGS. 27A-27C illustrates an alternative connection arrangement whereinoutward locking tabs on a prosthetic heart valve 20 mate withinwardly-facing channels in a sewing ring cuff 302. In general, thesewing ring cuff 302 contains a number of “female” bayonet mountingtracks and slots on its inner face while a ring connected to the heartvalve 20 features an equal number of “male” barb protrusions which lockinto the bayonet track. The conduit graft 22 attaches to the sewing ringcuff 302.

FIG. 27A shows some of the inner structural components of the heartvalve 20, including an inner polymer stent 304 having an undulating bandportion 306 with upwardly-projecting commissure posts 308. A metallicband 310 concentrically surrounds the stent 304 and also has anundulating shape, matching the undulating band portion 306. The stent304 and band 310 are normally included in the prosthetic heart valve 20.A third locking band 312 concentrically surrounds the metallic band 310.The locking band 312 has a relatively planar lower edge 314 andundulating upper edge 316 that tracks the undulating shape of themetallic band 310. A number of angled barbs 318 project outward from thelocking band 312. As seen in the sectional view of FIG. 29B, the barbs318 project outward from the structure of the valve 20. The valve mayinclude the stent 304, band 310, and locking band 312, or the barbs 318may be incorporated into the metallic band 310, such as shown in thecross-section of FIG. 29B.

The sewing ring cuff 302 has a series of suture holes 320 on itsexterior as well as a series of bayonet locking channels 322 thatmatched the barbs 318. Preferably, there are three barbs 318 and threebayonet locking channels 322. FIGS. 27B and 27C show engagement betweenthe heart valve 20 and its outwardly projecting barbs 318 and the sewingring cuff 302.

FIG. 28 illustrates the sewing ring cuff 302 above an outer anchoringmember 330 that forms a part of the lower end of a conduit graft. Theanchoring member 330 has a planar upper edge 332 and an undulating loweredge 334 with a plurality of suture holes therethrough. With referenceto the cross-section of FIGS. 29A and 29B, the anchoring member 330connects to both an outwardly extending sewing ring 336 via a fabricenclosure 338, and to the conduit graft 22 using sutures. The sewingring 336 is used to attach the valve conduit to the aortic annulus 340.At the same time, the sewing ring cuff 302 attaches to the inner face ofthe anchoring member 330 using sutures, as seen in FIG. 29A. Finally,the prosthetic heart valve 20 engages the sewing ring cuff 302 using thebarbs 318 and bayonet locking channels 322. Preferably, small matingramps within the locking channels 322 retain the barbs 318 therein. Asthe barbs 318 flex past the ramps, they snap into place.

Desirably, when the barbs 318 snap into the docking area of the lockingchannels 322 they retain a slight downward deformation and thus exert aforce between the sewing cuff and the valve body, thereby limitingrelative motion and ensuring a good seal between two. The barbs 318 andrespective channels 322 may be distributed non-uniformly in thecircumferential direction such that the valve and sewing cuff are“keyed” thereby eliminating the possibility of positioning the valveincorrectly once the sewing ring cuff 302 has been implanted.

In practice, the sewing ring 336 and conduit graft 22 assembly could besewn to the heart valve without the valve docked in place. This wouldallow the surgeon to have good visibility through the conduit into theventricle during suturing of the sewing ring 336 to the annulus.Alternatively, the valve may be engaged with the sewing ring cuff 302and then the entire assembly attached to the annulus/aorta. Theprosthetic heart valve 20 can thus be easily engaged and disengaged fromthe sewing ring cuff 302, which remains attached to the anchoring member330 and conduit graft 22, both of which are attached to the aorticannulus. Replacement of the valve in a redo operation would entailcreating an aortotomy in the conduit graft 22, unlocking the valve 20,then locking a new one in its place. Because the valve can easily beseparated from and reattached to the sewing ring cuff 302, the valve canbe supplied in glutaraldehyde and rinsed at the time of use, or suppliedin dry format.

FIG. 30 is a perspective view of a still further valved conduit 400wherein a conduit graft 402 and a prosthetic heart valve 404 areconnected utilizing an intermediate ring or band 406. In thisconfiguration, the conduit 402 is not directly attached to the valve404. The generally tubular band 406 is seen by itself in FIG. 31A, andincludes a circular upper edge 408 and a crenelated or crowned loweredge 410. The band 406 is desirably made of the same or similar materialas the conduit graft 402 (stiff fabric or a rigid or semi-rigid plasticmaterial) and pre-attached thereto by means of ultrasonic or vibrationwelding techniques. The lower edge of the conduit graft 402 can beplaced internally, externally, or flush to the upper edge 408 andsecured with welding, as mentioned, or with sutures as described below.A weld forms a robust hemostatic seal between the conduit graft 402 andband 406.

The subassembly of the conduit graft 402 and band 406 can then beattached to a sewing cuff 412 (or sewing ring) of the prosthetic heartvalve 404 by means of attachment sutures 414 passed back and forththrough a plurality of holes 416 in the band 406. The valve 404 may havea single or double sewing cuff 412, as described earlier. The holes 416act as a template indicating where to pass the sutures 414, and aredesirably distributed in a zig-zag pattern to enable the sutures toalternately pass through the conduit graft 402 and then the valve sewingcuff 412. The prongs of the crown-shaped lower edge 410 enable the band406 to expand around various sized sewing cuffs 412. Once assembled, thecompleted valved conduit 400 can then be attached to the aortic annulusby passing implant sutures through an outer sewing cuff 418 (theillustrated embodiment includes a double sewing cuff, though a singlesewing cuff may be used as well).

As seen best in FIGS. 30B and 30C, the band 406 features at least onecutting well 420 secured to its outer surface between two of the holes416. The cutting well 420 comprises a small plastic channel across whichthe suture 414 passes. Although not shown, a small notch on both sidesof the channel may be provided to hold the suture 414 in placeperpendicularly spanning the channel.

If the prosthetic heart valve 404 needs to be replaced for a redosurgery, it can be easily removed from the band 406 by inserting ascalpel into the cutting well 420 thereof and cutting the suture 410 toremove it. More than one cutting well 420 may be provided. This willfree the valve 404 from the band 406. The suture 410 is not tied to theband 406 so it can be removed with its loose ends simply pulling freefrom the band 406. The implant sutures connecting the valve sewing cuff418 to the annulus can then be removed utilizing a scalpel, thus freeingthe valve 404 from the annulus. A new valve can then be attached bypassing sutures through the holes 416 on the band 406, through thesewing cuff 412, and then implant sutures through the outer cuff 418 andannulus. For better visibility, the holes 416 may be ringed with coloredink or fabric, or grommets may be used for tactile feedback.

FIG. 31B illustrates an alternative intermediate band 428 for connectingthe conduit graft 402 and the prosthetic heart valve 404 that hascrown-shaped upper and lower edges, 429 a, 429 b in a so-called “doublecrown ring.” Again, the conduit 402 is not directly attached to thevalve 404, and the intermediate band 428 works with a valve 404 that hasa single or double sewing cuff or sewing ring. The band 428 attaches tothe conduit graft 402 initially by means of suturing techniques using aseries of holes 430 in a zig-zag pattern on the upper edge 429 a of thedouble crown band 428. The conduit graft 402 is desirably placedinternally to the double crown band 428. The double crown band 428 canbe made of a stiff fabric or a rigid or semi-rigid plastic material. Theband-to-conduit connection forms a robust hemostatic seal, which may beenhanced with a layer of silicone or other sealant therebetween. Thesubassembly of the conduit graft 402 and double crown band 428 can thenbe attached to the valve 404 by means of suturing thread utilizing aseries of holes 432 in a zig-zag pattern on the lower edge 429 b of thedouble crown band 428. The complete valved conduit is again attached tothe aortic annulus by passing implant sutures through the single sewingcuff or an outer sewing cuff if the valve assembly has a double sewingcuff.

As before, if the valve 404 needs to be replaced for a redo surgery, itcan be easily removed from the double crown band 428 by inserting ascalpel into a cut well 438 and cutting the suture to remove it. Thiswill free the valve 404 from the double crown band 428, and the implantsutures attaching the valve 404 to the annulus can be removed from thesewing cuff utilizing a scalpel, freeing the valve completely. A newvalve can then be attached by passing sutures through the holes 434 onthe lower edge 436 of the double crown band 428, then through the sewingcuff, and then implant sutures through the outer cuff and annulus.

FIGS. 32A-32D illustrate one embodiment of a subassembly of a conduitgraft and annular sewing ring connected together via an intermediateband. The sewing ring 440 desirably has a radial cross-section with acentral, generally vertical wall 441, and inner and outer ledges 442 a,442 b. A first embodiment of an intermediate band 443 in FIG. 32Aincludes a generally axial portion 444 a and a small lip 444 b thatprojects radially inward. The band 443 conforms to and fits closelyagainst an inner side of the vertical wall 441 of the sewing ring, andthe lip 444 b rests on the inner ledge 442 a. The band 443 is secured tothe sewing ring 440 by being insert molded with the inner core, or byultrasonic or vibration welding to the outer cloth covering. A secondembodiment of an intermediate band 445 shown in FIG. 32B includes agenerally axial portion 446 a and a small lip 446 b that projectsradially outward and rests on the outer ledge 442 b. Again, the band 445is secured to the sewing ring 440 by being insert molded therewith or bywelding.

FIG. 32C shows attachment of a lower end of a conduit graft 447 to thesewing ring 440 and second intermediate band 445. More specifically, alower collar portion 448 of the graft that extends downward from a seam449 is ultrasonic or vibration welded to an inner side of the band 445.The finished subassembly is seen in FIG. 32D. This method of attachmentcan be done with the first embodiment of the band 443 as well, with thecollar portion 448 of the graft being located on the inside of thevertical wall 441 of the sewing ring. Both assembly methods eliminatesuturing, which speeds up the process. The subassembly can then beindependently leak tested before a prosthetic valve is added to form avalved conduit.

FIG. 33A is a perspective exploded view of an alternative configurationof a valved conduit 450 including a conduit graft 452, a prostheticheart valve 454, and a sewing cuff or ring 456. FIG. 33B illustrates asubassembly of the sewing ring 456 attached to a lower end 458 of theconduit graft 452, with the prosthetic heart valve 454 attached to aholder 460 being lowered into an upper end 462 of the conduit graft. Aswill be explained in detail below, pre-attachment of the sewing ring 456to the conduit graft 452 facilitates the assembly process and enablesindependent leak checking of the graft prior to attachment of the heartvalve 454. For the sake of orientation, the sewing ring 456 is deemed tobe on a lower end of the graft 452, with the arbitrarily directions upand down defined thereby.

In one embodiment, the sewing ring 456 is the same sewing ring thatwould normally be attached to the prosthetic heart valve 454. The heartvalve 454 includes an internal support frame (not shown) that defines aplurality of alternative commissure posts 470 and cusps 472. The outeredges of three flexible leaflets 474 are secured along the cusps 472 andcommissure posts 470 and are supported thereby so as to meet or “coapt”across an outflow end of the valve. The support frame is covered with abiocompatible fabric, and a tubular segment 476 thereof extends downwardfrom the cusps 472. The tubular fabric segment 476 is used to attach theheart valve 454 to the sewing ring 456, as will be shown.

The holder 460 preferably includes a central hub 480 having three legs482 that radiate outward and are angled downward so as to be able tocontact the cusps 472 of the valve 454. The legs 482 of the holder 460may be sutured to the cloth covering the cusps 472, with the attachmentssutures extending back to the central hub 480 to a central cutting well(not shown). In this way, the assembler can deliver the heart valve 454through the interior of the conduit graft 452, secure it, and use theholder for delivery of the valved conduit 450. In this regard, theholder 460 has sufficient length to extend from the heart valve 454 outof the outflow end of the conduit graft 452. After implanting the valvedconduit 450, the surgeon releases the holder 460 from the valve 454 bycutting the attachments sutures (preferably with one cut). Prior toinserting the heart valve 454 into the upper end 462 of the graft 452,the tubular fabric segment 476 is rolled upward and secured with one ormore sutures to form a temporary cloth tab 484. This facilitates thepassage of the heart valve 454 through the graft 452. Specific steps forattaching the heart valve 454 to the sewing ring 456 are provided belowwith respect to FIGS. 36-37.

FIGS. 34-35 are a number of steps for pre-assembling the sewing ring 456to the conduit graft 452. FIG. 34A shows the lower end of the graft 452within and adjacent to the sewing ring 456. As described previously, theconduit graft 452 comprises an enlarged region or bulge 486 designed toconform to the sinuses of valsalva just above the aortic annulus. In thepreferred embodiment, the conduit 452 comprises a tubular textilestructure, such as Dacron, sealed with a bioresorbable medium. Withreference back to FIGS. 33A-33B, a major length 488 of the conduit graft452 includes a corrugated structure with circumferential grooves 490that provide lateral flexibility while ensuring that the conduit willnot unduly radially compress or expand under the pressure of bloodflowing therethrough. The major length 488 is desirably a fewcentimeters to 10-12 centimeters long. The bulge 486 has corregationsthat run longitudinally to enable that region to be radially expanded. Alower collar portion 492 attaches to the bulge 486 at a seam 494. Theseam 494 is shown schematically in the sectional views for clarity. Asseen in FIG. 33A, the lower collar portion 492 is trimmed and so as tohave an undulating shape that matches the undulating shape of the sewingring 456.

With reference back to FIG. 34A, the sewing ring 456 includes an innersuture-impermeable core 496 surrounded by a biocompatible fabriccovering 498. As described previously, the sewing ring 456 desirably hasa radial cross-section with a distorted T-shape formed by a central,generally vertical wall 500, an outer flange 502, and an inner ledge504. Both the outer flange 502 and the inner ledge 504 connect to alower end of the central vertical wall 500 and project in oppositedirections therefrom. The outer flange 502 extends outward at a slightupward angle, and preferably connects to the vertical wall 500 via aseries of circumferentially-oriented ribs which define open cellstherebetween (such as shown above in FIG. 5). The inner ledge 504extends generally radially inward and has no such ribs. As mentioned,the sewing ring 456 desirably has an undulating shape with alternatingpeaks and valleys that ultimately correspond to features on theprosthetic heart valve 454. The lower collar portion 492 of the conduitgraft 452 extends within the vertical wall 500 and inward along theinner ledge 504. The termination of the collar portion 492 conformsclosely with the undulating shape of the inner ledge 504.

FIG. 34B shows a number of outward force arrows 510 directed to theinside of the conduit graft 452. These force arrows 510 represent theforce that would be applied by a rigid mandrel (similar to that shown inFIG. 35B) inserted within the conduit graft 452. Desirably, the mandrelis large enough so as to slightly expand the flexible sewing ring 456.FIG. 34B also indicates in phantom an extension of the collar portion492 so that it wraps around the inner end of the inner ledge 504 of thesewing ring 456, which may help seal the border between the graft 452and sewing ring.

FIG. 34C shows the process of forming a seam along the upper edge of thesewing ring 456, connecting it with the conduit graft 452. Inparticular, a needle 512 passes through the vertical wall 500 andthrough the seam 494 of the conduit graft 452. One of the stitches 514is shown at the desired location in FIG. 34D. A series of the stitches514 are sewn around the circumference between the conduit graft 452 andsewing ring 456 to form a seam. Preferably, the needle 512 does notpierce the wall of the conduit graft 452 so as to minimize blood leakagetherethrough.

FIGS. 35A-35C illustrate the process of forming a second seam comprisinga plurality of stitches 520 between the conduit graft 452 and sewingring 456. In particular, a mandrel 522 seen in the upside-down view ofFIG. 35B again applies an outward force on the collar portion 492against the inside of the sewing ring 456. Once again, the mandrel 522is preferably large enough so as to slightly outwardly stretch thesewing ring 456. Another needle 524 is then used form the stitches 520between the terminal end of the collar portion 492 and the inner edge ofsewing ring inner ledge 504. In one embodiment, the mandrel 522 issegmented at the uppermost end as seen in FIG. 35B so as to provide aseries of gaps around the circumference through which the needle 524 canbe passed. This provides a guide to where the stitches 520 are placed.The series of stitches 520 as seen in FIG. 35C forms a lower seambetween the conduit graft 452 and sewing ring 456 and completes thesubassembly. The mandrel 522 is then removed.

At this point, the completed subassembly of the conduit graft 452 andsewing ring 456 can be independently leak tested. More particularly, aleak test with the same fluid media that the maker of conduit graft 452uses can be done. Pulsatile testing with saline is commonly done forsuch grafts. This is not possible once the heart valve 454 has beenincorporated. If necessary, additional coatings (silicone, gelatin,hydrogel, etc.) to seal the holes caused by forming the stitches can beapplied without fear of exposing the heart valve 454 and itsbioprosthetic leaflets 474.

Another advantage of separating the sewing ring 456 from the remainderof the prosthetic heart valve 454 is the ability to customize eachvalved conduit 450. More particularly, for many commercial heart valvesthe majority of the valve components across all models are the same, andit is the sewing ring that differentiates them. Different heart valvemodels can thus be coupled to the same subassembly of the sewing ring456 and conduit graft 452. This is a much more flexible manufacturingprocess and inventory control. Moreover, without the sewing ring 456attached, the number of fixtures needed to do flow and leak testing ofthe valve 454 is simplified. Current valve flow and leak testers havedifferent fixtures for all of the valve models to conform to thedifferent sewing ring geometries. By removing the sewing ring 456, allof the prosthetic heart valves configured as in FIG. 33A would have thesame “temporary” cloth sewing ring and therefore only one fixture foreach size would be needed.

FIG. 36A illustrates the prosthetic heart valve 454 connected to theholder 460 within the lower end of the subassembly of the conduit graft452 and sewing ring 456 cut away. As mentioned above, the assembleradvances the valve 454 through the subassembly until a lower or inflowend of the valve 454 aligns with the sewing ring inner ledge 504, asindicated by a comparison of FIGS. 36B and 36D. The holder 460 can beremoved at this point, but is preferably left in place during thesubsequent sewing steps and used for delivery of the valved conduit 450.

The heart valve 454 desirably has an inner leaflet support frame coveredwith fabric that defines a flow orifice, such as described above withrespect to FIG. 4A. Again, the inner support frame preferably includes astent with two concentric bands that are enclosed in fabric which isbunched or rolled into an outwardly-directed sewing tab. The outer edgesof the leaflets are sandwiched between the top of the stent structureand the bottom of a cloth-covered wireform that may have a sewing flapas shown. Of course, this particular type of heart valve isrepresentative of many others.

FIG. 36C shows the unfinished assembly upside-down with the tubularfabric segment 476 extending beyond the sewing ring 456. A needle 530 isshown passing a suture through the fabric segment 476 and the innerledge 504 of the sewing ring 456. The positioning of stitches 532between these two components is seen in FIG. 36D.

FIGS. 37A-37D illustrate formation of a second seam between the conduitsubassembly and the heart valve 454. First, as seen in FIG. 37A, excesstubular cloth from the fabric segment 476 is trimmed and/or folded tocreate an even edge 534. The assembler then folds the fabric segment 476against the underside of the sewing ring 456. Temporary means forholding the fabric segment 476 flush against the sewing ring 456, suchas pins or the like, may be used. FIG. 37B shows a needle 536 passedthrough the outermost edges of the outer flange 502 of the sewing ring456 and the fabric segment 476 creating a series of stitches 538 thattogether define a seam, as best seen in FIG. 37D. The lower end of thefinished valved conduit 450 is shown in FIG. 37C.

The valved conduit 450 with the holder 460 attached to the valve 454 isthen packaged in a sterile container and stored until needed. Asmentioned above, the heart valve 454 is desirably a “dry” valve that canbe stored with a conduit graft 452 sealed with a bioresorbable mediumsuch as gelatin or collagen. This process produces a valved conduit thatis ready for implantation without the need for a clinical rinse insaline, thereby shortening implant time. Furthermore, the handle 460remains attached and is thus ready to use during the implant procedure.Preferably the handle 460 has a length sufficient to extend out of thetop end of the conduit graft 452. The surgeon manipulates the valvedconduit 450 into place using the handle 460, and secures the sewing cuff418 of the valve to the annulus. At any time, the holder 460 can beremoved to help with visibility of the interior of the valve 454.

FIG. 38 shows an alternative type of stitch that may be used between theconduit graft 452 and sewing ring 456. Desirably, whip stitches 520 asshown in FIG. 35C are used due to the ease of assembly. Alternatively, amanual in-and-out stitch 540 as shown in FIG. 38 may be used.Furthermore, an in-and-out stitch 540 can be applied by an automated orrobotic sewing machine.

FIG. 39 shows the addition of a sealant 542 interposed between theconduit graft 452 and sewing ring 456. As mentioned, a sealant such assilicone or adhesive can be used in various places between thecomponents of the valve conduit 450, but an especially importantlocation is between the collar portion 492 of the conduit graft 452 andthe vertical wall 500 of the sewing ring 456. Although both stitcheslower and upper stitches 514 and 520 are shown in FIG. 39, it should beunderstood that one or even both of them may be omitted if a suitableadhesive is used between the opposing surfaces.

FIGS. 40A and 40B show still further alternative stitches that may beused between the conduit graft 452 and sewing ring 456. First, FIG. 40Aindicates a radial in-and-out stitch 550 at the location of the verticalwall 500 of the sewing ring 456. Although this stitch is an alternative,it may provide an avenue for leakage as indicated and preferably is usedin conjunction with a sealant or adhesive between the two surfaces.Likewise, FIG. 40B illustrates a stitch 552 at the top of the verticalwall 500 that penetrates through the conduit graft 452, as opposed tojust through the seam 494. Penetrating the conduit graft 452 introducesan avenue for leakage, and thus this type of stitch 552 should be usedin conjunction with a sealant.

FIGS. 41 and 42 schematically illustrate a process for shaping tissue toform an aortic root portion of a conduit graft. Fabric grafts presentrelatively large surface area of biomaterial in contact with blood.Sometimes this fabric is never completely covered with pannus resultingin need for anticoagulant therapy for many patients. Moreover, fabricconduits tend to seep plasma until clotted. One possible solution is toform the graft from tissue, minimizing thrombolysis and thromboembolismand reducing seepage. For example, the tissue sheet may be formed into atube or other graft shape to replace the conduit graft described herein.

Moreover, the tissue graft may be shaped to provide the sinus portion ofthe ascending aortic graft. For example, an inner mandrel 560 may becombined with an outer mold half 562 as seen in FIG. 41 to sandwichtherebetween a sheet of tissue 564. The tissue is wrapped around theinner mandrel 560, and then upper half 566 of the mold is combined as inFIG. 42. The mold assembly is shaped to reflect the desired finalgeometry of the tissue, such as to replicate the geometry of the aorticroot complete with sinuses. The mold and tissue are placed into afixative solution (glutaraldehyde, formaldehyde, etc.) for fixation. Ifnecessary, the fixation fluid can be pressurized to facilitate diffusionthrough the tissue and mold. After fixation, the sheet of tissue 564 maybe sewn into a tube and other necessary structures attached, such assewing cuffs. Various types of tissue can be used, including human oranimal pericardium, dura mater, fascia latta, or other such sheettissue.

The tissue graft described above can be supplied wet, stored inglutaraldehyde, or can be dried as described herein. A dry sinus graftwould enhance handling, eliminate the need for extended rinsing, andcertain treatments will reduce the risk of calcification in the graftcomponent.

One aspect of the present application provides techniques for couplingimplantable valves with conduits, and in particular bioprosthetic heartvalves that have been dried and are not stored immersed in apreservative solution. The term “dried” or “dry” bioprosthetic heartvalves refers in general to the ability to store those heart valveswithout immersion in solution (e.g., a preservative likeglutaraldehyde), and in particular to dry storage for extended periodswithout degradation of functionality of the bioprosthetic valve. Thereare a number of proposed methods for drying bioprosthetic heart valves,and for drying tissue implants in general, and the present applicationencompasses bioprosthetic heart valves that are processed by any ofthese methods.

One strategy for drying tissue is to dehydrate the bioprosthetic tissuein a glycerol/ethanol mixture, sterilize with ethylene oxide, andpackage the final product “dry.” This process eliminates the potentialtoxicity of glutaraldehyde as a sterilant and storage solution. Therehave been several methods proposed to use sugar alcohols (i.e.,glycerine), alcohols, and combinations thereof as post-glutaraldehydeprocessing methods so that the resulting tissue is in a “dry” staterather than a wet state with excess glutaraldehyde. Glycerol-basedmethods can be used for such storage, such as described in Parker et al.(Thorax 1978 33:638). A particularly preferred method of dryingbioprosthetic heart valves is disclosed in U.S. Pat. No. 8,007,992 toTian, et al. (the disclosure of which is expressly incorporated hereinby reference) wherein fixed tissue is treated with a non-aqueous mixtureof glycerol and C₁-C₃ alcohol selected from the group consisting ofmethanol, ethanol, n-propanol, 2-propanol. Likewise, U.S. Pat. No.6,534,004 (Chen et al.) describes the storage of bioprosthetic tissue inpolyhydric alcohols such as glycerol. In processes where the tissue isdehydrated in an ethanol/glycerol solution, the tissue may be sterilizedby ethylene oxide (ETO), gamma irradiation, or electron beamirradiation.

More recently, Dove, et al. in U.S. Pat. No. 7,972,376, issued Jul. 5,2011, propose solutions for certain detrimental changes withindehydrated tissue that can occur as a result of oxidation, thedisclosure of which is expressly incorporated herein by reference. Dove,et al. propose permanent capping of the aldehyde groups in the tissue(reductive amination). One preferred anticalcification tissue treatmentincludes applying a calcification mitigant such as a capping agent or anantioxidant to the tissue to specifically inhibit oxidation indehydrated tissue and reduce in vivo calcification. The treatmentspecifically caps aldehyde groups in crosslinked (e.g., withglutaraldehyde) bovine, porcine, or equine pericardial tissue or aporcine valve. In one method, tissue leaflets in assembled bioprostheticheart valves are pretreated with an aldehyde capping agent prior todehydration and sterilization. Dove, et al. also describe the additionof chemicals (e.g. antioxidants) to the dehydration solution (e.g.,ethanol/glycerol) to prevent oxidation of the tissue duringsterilization (ethylene oxide, gamma irradiation, electron beamirradiation, etc.) and storage. The capping process uses an amine, forexample ethanolamine or lysine, and a reducing agent, followed by finalprocessing with glycerol and an alcohol. The capping agent may beselected from the group consisting of: an amine, an amino acid, and anamino sulfonate. The reducing agent may be a borohydride, for examplesodium borohydride or cyanoborohydyride. Other reducing agents include:sodium bisulfite+acetylacetone, and formic acid+formaldehyde.

These and other methods for drying bioprosthetic heart valves are usedprior to coupling of the valve with the conduit. The removal of apercentage of water from the valve and replacement with glycerol andethanol allows the device to be stored “dry” (i.e. glycerolized). The“dry” valve may then be sewn into the polyester or tissue conduit orgraft and be ready for implantation. This process allows making a valvedconduit that is ready for implantation without the need for a clinicalrinse in saline, thereby shortening implant time. For purpose ofdefinition, a “dry” bioprosthetic tissue is one with less than 70% watercontent. In terms of practical rehydration, functional valves have atleast 70% water content. The most important distinction of “dry” valves(or tissue therein), however, is that they may be stored dry forextended periods (sometimes years) without degradation of functionalityof the valve.

A number of exemplary bioprosthetic heart valves and conduits are shownand described in the present application. Each of these different typesof heart valves may be processed so that they are stored dry. The readerwill understand that the present methodologies apply to any and allbioprosthetic valves that are stored dry, and are not limited to thoseexemplary valves shown herein. In particular, prosthetic heart valvesfor implant at any of the four native valve annuluses—aortic, mitral,pulmonary, and tricuspid—may be dried and stored in accordance with theprinciples described herein. Alternatively, valved conduits produced inaccordance with the principles disclosed herein may be used in locationsother than heart valve replacement, such as venous valves by connectinga small bileaflet valve to or within a small diameter conduit.

Additionally, a number of techniques for packaging the dry bioprostheticheart valves and their delivery systems are possible. In general, abioprosthetic heart valve must be stored in sterile conditions, whichrequires at least one sterile container. Preferably, however, adual-barrier packaging system is used to reduce the chance ofcontamination of the implant at the time of surgery. For instance, U.S.Patent Publication No. 2011/0147251 to Hodson, et al. disclosesexemplary packaging systems which can be utilized, the contents of whichare hereby expressly incorporated herein.

The present application describes systems and methods for pre-assemblingand storing a bioprosthetic heart valve and conduit to form the valvedconduit. The term “pre-assembling” or “pre-assembled” refers toconnection of the heart valve and conduit prior to the operating roomtechnicians opening the sterile packaging. In other words, the valvedconduit emerges mechanically assembled from the packaging, substantiallyready for delivery (after any pre-surgery washing or other suchpreparation).

While the invention has been described in its preferred embodiments, itis to be understood that the words which have been used are words ofdescription and not of limitation. Therefore, changes may be made withinthe appended claims without departing from the true scope of theinvention.

What is claimed is:
 1. A method of assembling a valved conduit,comprising: forming a subassembly of a fabric conduit graft and anannular sewing ring, the conduit graft comprising a longitudinal tubularportion between an upper end and a lower end, the lower end having acollar portion, the sewing ring comprising an inner core and an outerfabric covering, the step of forming comprising positioning the sewingring adjacent the lower end of the conduit graft so that the collarportion contacts an inner wall of the annular sewing ring and securingthe collar portion thereto; leak testing the subassembly of the conduitgraft and sewing ring; providing a prosthetic heart valve having aninner support frame covered with fabric and defining a flow orifice anda plurality of leaflets extending inward from the support frame toensure one-way blood flow through the heart valve, the fabric coveringthe support frame extending downward in a tubular segment; attaching aholder to the heart valve; and positioning the heart valve within thelower end of the leak tested subassembly of the conduit graft and sewingring and folding the tubular segment of the fabric covering radiallyoutward underneath the subassembly and secured the tubular segmentthereto with sutures, the holder having a length sufficient to extendfrom the heart valve out of the upper end of the conduit graft.
 2. Themethod of claim 1, wherein the collar portion has an undulating shapearound its circumference with peaks and valleys, and the sewing ringalso has an undulating shape around its circumference with peaks andvalleys, wherein the peaks and valleys of the collar portion align withthe peaks and valleys of the sewing ring.
 3. The method of claim 1,including securing the conduit graft to the sewing ring using sutures.4. The method of claim 1, including securing the conduit graft to thesewing ring by welding.
 5. The method of claim 1, wherein the heartvalve leaflets are made of bioprosthetic tissue.
 6. The method of claim5, wherein the conduit graft comprises a tubular matrix impregnated withgelatin.
 7. The method of claim 5, wherein the heart valve leaflets areformed of bovine pericardium that has been cross-linked usingglutaraldehyde or other aldehyde containing agents, treated with acapping agent, and is dehydrated with a glycerol solution.
 8. The methodof claim 1, wherein the step of leak testing the subassembly includespulsatile testing with saline.
 9. A method of assembling a valvedconduit, comprising: forming a subassembly of a fabric conduit graft andan annular sewing ring, the conduit graft comprising a longitudinaltubular portion between an upper end and a lower end, the lower endhaving a collar portion, the sewing ring comprising an inner core and anouter fabric covering, the step of forming comprising positioning thesewing ring adjacent the lower end of the conduit graft so that thecollar portion contacts an inner wall of the annular sewing ring andsecuring the collar portion thereto; leak testing the subassembly of theconduit graft and sewing ring; providing a prosthetic heart valve havingan annular support frame covered with fabric but without a sewing ringattached thereto and flow-occluding leaflets mounted within the supportframe; positioning the prosthetic heart valve within the lower end ofthe leak tested subassembly of the conduit graft and sewing ring, withthe annular support frame adjacent to and in contact with the inner wallof the annular sewing ring; and securing the prosthetic heart valvewithin the lower end with sutures between the fabric covering theannular support frame and the annular sewing ring.
 10. The method ofclaim 9, wherein the collar portion has an undulating shape around itscircumference with peaks and valleys, and the sewing ring also has anundulating shape around its circumference with peaks and valleys,wherein the peaks and valleys of the collar portion align with the peaksand valleys of the sewing ring.
 11. The method of claim 9, includingsecuring the conduit graft to the sewing ring using sutures.
 12. Themethod of claim 9, including securing the conduit graft to the sewingring by welding.
 13. The method of claim 12, wherein the conduit graftcomprises a tubular matrix impregnated with gelatin.
 14. The method ofclaim 9, wherein the prosthetic heart valve leaflets are formed ofbovine pericardium that has been cross-linked using glutaraldehyde orother aldehyde containing agents, treated with a capping agent, and isdehydrated with a glycerol solution.
 15. The method of claim 9, whereinthe step of positioning the prosthetic heart valve comprises: attachinga holder to the prosthetic heart valve, the holder having a lengthsufficient to extend from the prosthetic heart valve out of the upperend of the conduit graft; and advancing the holder with the prostheticheart valve attached through the upper end of the conduit graft.
 16. Themethod of claim 9, wherein the fabric covering the support frame extendsdownward in a tubular segment, and the step of securing the prostheticheart valve includes folding the tubular segment of the fabric coveringradially outward underneath the subassembly and secured the tubularsegment thereto with sutures.
 17. The method of claim 9, wherein thestep of leak testing the subassembly includes pulsatile testing withsaline.
 18. A method of assembling a valved conduit, comprising: forminga subassembly of a fabric conduit graft and an annular sewing ring, theconduit graft comprising a longitudinal tubular portion between an upperend and a lower end, the lower end having a collar portion, the sewingring comprising an inner core and an outer fabric covering, the step offorming comprising positioning the sewing ring adjacent the lower end ofthe conduit graft so that the collar portion contacts an inner wall ofthe annular sewing ring and securing the collar portion thereto; leaktesting the subassembly of the conduit graft and sewing ring; providinga prosthetic heart valve having an annular support frame covered withfabric but without a sewing ring attached thereto and flow-occludingleaflets mounted within the support frame; positioning the prostheticheart valve within the lower end of the leak tested subassembly of theconduit graft and sewing ring, with the annular support frame adjacentto and in contact with the inner wall of the annular sewing ring; andsecuring the prosthetic heart valve within the lower end with suturesbetween the fabric covering the annular support frame and the annularsewing ring, wherein the prosthetic heart valve has a fabric covering asupport frame that extends downward in a tubular segment, and the stepof securing the prosthetic heart valve includes folding the tubularsegment of the fabric covering radially outward underneath thesubassembly and secured the tubular segment thereto with sutures.